Public bug reported:
After logout, SDDM immediately restarts the greeter, which launches
kwin_wayland as its compositor. kwin_wayland successfully obtains a DRM
file descriptor from logind via TakeDevice, but then tries to ::open()
the same DRM node directly. This direct open fails because the sddm
user's logind ACLs haven't been fully updated yet from the previous
session teardown. kwin_wayland exits, the greeter dies, and SDDM doesn't
restart it because HELPER_SUCCESS wasn't treated as a failure.
This is fixed with three patches:
SDDM:
- fix-vt-hang-on-logout.patch: Fix SDDM hanging on logout by
resetting VT from VT_PROCESS to VT_AUTO when the controlling session
process has exited, preventing VT_WAITACTIVE from blocking
indefinitely.
- fix-greeter-restart-on-crash.patch: Restart greeter when it
exits unexpectedly (e.g. compositor crash). SDDM now distinguishes
between an intentional greeter stop (user login via expectStop(),
explicit stop()) and an unexpected exit, emitting the failed() signal
in the latter case so the display is restarted. Display calls
expectStop() on the greeter when user authentication succeeds to
prevent the normal session-handoff exit from being treated as a
crash.
kdm:
- fix-drm-open-fallback-to-logind-fd.patch: Fall back to logind
file descriptor when direct DRM node open fails. Fixes SDDM greeter
compositor failing to start after logout because sddm user lacks
filesystem-level permissions on /dev/dri/card* during session switch.
** Affects: kwin (Ubuntu)
Importance: Critical
Assignee: Erich Eickmeyer (eeickmeyer)
Status: In Progress
** Affects: sddm (Ubuntu)
Importance: Critical
Assignee: Erich Eickmeyer (eeickmeyer)
Status: In Progress
** Tags: resolute
** Changed in: sddm (Ubuntu)
Importance: Undecided => Critical
** Also affects: kwin (Ubuntu)
Importance: Undecided
Status: New
** Changed in: kwin (Ubuntu)
Status: New => In Progress
** Changed in: kwin (Ubuntu)
Importance: Undecided => Critical
** Changed in: kwin (Ubuntu)
Milestone: None => ubuntu-26.04
** Changed in: kwin (Ubuntu)
Assignee: (unassigned) => Erich Eickmeyer (eeickmeyer)
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https://bugs.launchpad.net/bugs/2147233
Title:
sddm and kwin have race condition with logout
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